1. Field of the Invention
The present invention relates generally to connectors which can be mated and unmated in a harsh environment, such as underwater, and is particularly concerned with a harsh environment electrical or hybrid connector.
2. Related Art
Since about the early 1960's, connectors that could be mated and de-mated in harsh environments, particularly underwater, have been commercially available. The earliest of these was a rubber-bodied pin-and-socket connector that embodied one or more ring-like contacts molded into a cylindrical rubber pin, and respective one-or-more ring-like contacts molded into a rubber bore. These connectors have the advantage that the two mating halves require no particular rotational alignment. For that reason, they are said to be keyless.
These connectors are relatively inexpensive, but not reliable enough for most critical applications. They have the distinct disadvantage that they cannot be unmated underwater except at very modest depths; and, in models having more than one set of contacts arranged along the pin and bore, cross-connection briefly takes place as un-matched pin and socket contacts slide past each other during mating and de-mating. Cross-connecting circuits can sometimes be disastrous for the electronics to which they are attached. In spite of these shortcomings, these connectors are still widely used today.
In the early 1970's a more dependable sort of harsh-environment connector was introduced (U.S. Pat. No. 3,643,207). The plug portion consisted of multiple pins with electrically insulated shafts and conductive tips. The receptacle had corresponding socket contacts in an oil-filled chamber. The chamber's internal pressure was balanced to that of the outside environment by way of a flexible wall. The male and female electrical junctions made contact within the electrically insulating oil, completely isolated from the outside environment. One example of this type of oil-filled connector is described in U.S. Pat. No. 3,643,207 of Cairns.
These oil-filled connectors were remarkably more reliable than the earlier rubber-molded ones. They were also more expensive. They were not accepted commercially for two main reasons: In those days they were untried technology, and, because of the multiple pins, they required rotational alignment. When multiple-pin connectors are mated, three orientation elements must be controlled: axial tilt, axial offset, and rotational alignment. The last of these is generally the most difficult to manage.
The offshore oil and gas industry is one of the principal markets for underwater mateable connectors. Many of the connectors used for that industry's subsea operations are connected and disconnected remotely, either by being mounted to large, opposed plates (stab plates) that come together during the mating process to join arrays of connectors, hydraulic couplers, and the like, or by the manipulators of remotely operated vehicles (ROV's). Mating remotely is made more difficult and expensive by the requirement to control the rotational alignment of the individual components to be mated.
In the early 1980's two-contact fluid-filled electrical connectors that required no rotational alignment were made commercially available. One example of such a connector is described in U.S. Pat. No. 4,606,603 of Cairns. These connectors did not immediately overcome customer reluctance to accept oil-filled technology, but they did solve the rotational alignment problem. They quickly became the offshore industry's standard for high-reliability operations, and remained so for the next decade.
The plug of the two-contact, fluid-filled connector consisted of one elongated, insulated pin that housed two coaxially disposed contacts. The corresponding receptacle contacts were contained in a flexible-walled, fluid-filled chamber. The chamber had a circular, elastic, penetrable opening in the anterior end that, in the unmated condition, was squeezed tightly shut by a rubber sphincter. The connectors had some problems. One problem was that two contacts were not enough to satisfy the needs of most operations. Another problem was that the receptacle's circular end-opening, which had to be pinched tightly closed before and after mating, had to be stretched several hundred percent to receive the plug's pin. If mated for a long time, particularly at low ocean temperatures, the opening did not close upon de-mating, and the connector subsequently failed.
As time went on more contacts, as many as six, were staged on to a conical portion of the plug's tip, and likewise their counterparts were added to the receptacle. Because of spatial constraints, this arrangement unacceptably diminished the connector's reliability. Modern specifications for connectors of the fluid-filled type require at least one, and preferably two, sealed insulating barriers, usually rubber, between each set of mated pin/socket contacts and every other set; and furthermore, between each set and the outside environment. The redundant barriers are a precaution in case of a single-seal failure. Although the two-contact version of the above keyless coaxial connector did have one seal between contact sets in the mated condition, the six-contact version had none. It was not possible to increase the plug pin's diameter further to make space for seals. Because the receptacle's penetrable opening had to close tightly when unmated, its at-rest size had to be small; and could not be increased. It was already stretched beyond acceptable limits when mated, so there was no way to up-size the pin.
In the late 1980's, multiple pin, fluid-filled connectors were once again introduced. They have all the required barriers, are robust, and exceptionally reliable. One such connector is the subject of U.S. Pat. No. 4,948,377 of Cairns. These connectors are manufactured by Teledyne ODI. They replaced the two-contact, single pin fluid-filled connectors described above as the high-reliability standard for the offshore industry. These connectors still have the rotational alignment problem, however, which somewhat limits their use, and require special keying provisions for rotational alignment.
In the early 1990's a keyless, coaxial, oil-filled, wet-mateable connector was introduced that required no rotational alignment. This connector is described in U.S. Pat. No. 5,171,158 of Cairns (hereinafter '158 patent). It consisted of multiple ring-like contacts spaced along a constant diameter portion of the plug pin. The receptacle had corresponding ring-like contacts spaced along a rubber bore to receive the plug contacts. The overall layout of the contacts was very similar to the first type of connector described above. The main differences were that the connector of the '158 patent housed the receptacle contacts in a pressure-balanced, fluid-filled chamber; and, when mated, the individual pin/socket pairs were separated from each other by a single rubber seal. Unlike the coaxial connector of U.S. Pat. No. 4,606,603 (hereinafter '603 patent), the anterior sealed opening through which the plug's probe passed when entering the receptacle's chamber was occupied by a spring loaded piston before and after mating. That removed the necessity of the sealed opening to be pinched closed to a zero diameter as in the '603 patent.
The connector shown in the '158 patent was reasonably successful technically and quickly gained a dedicated customer base, but it was discontinued after being on the market for just a couple of years. It proved to be too expensive and difficult to manufacture. It also still had the problem of cross-connection during mating and de-mating as the plug's contacts wiped across receptacle contacts which were not their intended counterparts.
The need for a keyless, reliable, wet-mateable connector still remains unfulfilled.